That's not what this case illustrates.

Here, the legislative body (the school board, a stand-in for Congress) apparently wrote a sloppily phrased rule (read, "law") that failed to distinguish between candy-filled vending machines and a kid who swapped a bag of Skittles to another kid.

So, a "judge" (school administrator) inherited the responsibility to clean up the mess. That is, he/she had to decide that the rule meant this, and not that.

What you call "writing law from the bench" is the job of a judge.

__________________
"The whole modern world has divided itself into Conservatives and Progressives. The business of Progressives is to go on making mistakes. The business of the Conservatives is to prevent the mistakes from being corrected." G.K. Chesterton